1. Field of the Invention
The present invention relates to a method for charging a lead lead-acid battery, and in particular to a method for charging a rechargeable closed lead lead-acid battery.
2. Description of the Related Art
There are various methods for charging lead lead-acid batteries, for example, constant-voltage charging, quasi-constant-voltage charging, constant-current charging, and joggle charging (pulse charging). These charging methods are carried out so as to obtain an appropriate charging state without any charge insufficiency or charge excessiveness, so that the cycle life feature of the lead lead-acid battery is fully utilized.
Hereinafter, a conventional, general method for charging a cell will be described. FIG. 11 shows a charging pattern obtained by a two-stage constant-current charging system using a conventional timer control. In FIG. 11, during a second-stage charging time period tC, charging is performed at a current of 0.1 CA. During the time period tC, a constant quantity of electricity is supplied to a lead lead-acid battery by a timer in which a charging time period is pre-set, regardless of a quantity of electricity discharged before charging. As a result, there is an undesirable possibility that the lead lead-acid battery is excessively charged when a small quantity of electricity is discharged before charging, and is insufficiently charged when a large quantity of electricity is discharged before charging. These undesirable effects result from the difficulty in setting an appropriate charging time period tC in the timer.
FIG. 12 shows a charging pattern obtained by a constant-voltage charging system. According to this system, it is possible to automatically supply a quantity of electricity corresponding to the quantity of electricity discharged before charging. However, since the quantity of chargeable electricity is automatically restricted by a receivable electricity quantity of each of lead lead-acid batteries, the lead lead-acid batteries tend to be slightly insufficiently charged. Thus, the cycle life feature of the lead lead-acid batteries cannot be fully utilized.
The present invention has objectives of solving such insufficient charging caused by a constant-voltage charging system, solving a problem of a timer-system constant-current charging system in that a constant quantity of electricity is supplied to a lead lead-acid battery regardless of the quantity of electricity discharged before charging, and providing a charging method for performing appropriate charging of the lead lead-acid battery without any insufficiency or excessiveness.